Fail-safe performance of devices plays a large role in medical technology; for example because during a surgical procedure, it cannot be interrupted simply because a medical device fails. Partially redundant illumination systems are therefore known in which multiple light sources are provided, such that upon failure of one light source it is possible to switch over to another light source. This is as a rule accompanied by a change in the beam path of the light, with the result that the light intensity also changes and the perception of the illuminated region can thus be different. Also known, alternatively, are illumination systems in which partial redundancy is achieved by the fact that a substitute light source can be swung in in place of another light source.
These partially redundant illumination systems are disadvantageous in that fail-safe performance is ensured only upon failure of the light source itself. On the other hand, in the event of failure of other modules of the illumination system that are essential for operation of the illumination system, for example the light source cooling system and/or the power supply system, the illumination system cannot continue to operate.
To solve this problem, illumination systems are known in which two entirely separate illumination units are provided, i.e. not only are two or more light sources provided, but all the other units are also provided in duplicate. Here each light source and the other associated elements constitute a respective autonomous unit. Such illumination units are disadvantageous in that they are of very complex construction and also function only as long as all the elements within one of these autonomous units are functional. For example, if the light source fails inside one unit, and the cooling system in the other unit, this illumination system as well can no longer be used.
Partially autonomous illumination systems of this kind are known, for example, from the documents DE 10 2004 051 940 A1, DE 4231469 A1 and DE 4104609 A1.